Cracks that form within polymeric composites can be difficult to detect and almost impossible to repair. A successful method of autonomically repairing cracks which has the potential for significantly increasing the longevity of the material has been described in U.S. Pat. No. 6,518,330, as well as in publications.1-5 This self-healing system includes a material containing, for example, solid particles of Grubbs' catalyst and capsules containing liquid dicyclopentadiene (DCPD) embedded in an epoxy matrix (FIG. 1A). When a crack propagates through the material, it ruptures the microcapsules and releases DCPD into the crack plane. The DCPD then mixes with the Grubbs' catalyst, undergoes Ring Opening Metathesis Polymerization (ROMP), and cures to provide structural continuity where the crack had been.
This system performs well with a relatively large (2.5 wt %) loading of catalyst, but multiple factors have made lower catalyst loadings less effective. First, the catalyst does not disperse well in the epoxy, so very few (but relatively large) catalyst particles are present on the crack plane when low catalyst loadings are used. Second, the epoxy's curing agent, diethylenetriamine (DETA), destructively attacks Grubbs' catalyst.2 A system where the catalyst is distributed better, and without exposing it to DETA, would allow more efficient use of the catalyst.